This invention relates to a thread movement sensor, comprising an arm with at least one thread guide.
There are known small diameter circular knitting machines which are provided with mechanical tension sensors. In such devices, in a certain zone of knitting of the fabric, the presence or the movement of the thread is detected by displacement of contact wires, which in case the thread is broken, closes an electric circuit whereby to cause a switching-off of the motor of the machine drive. The disadvantage of such known sensor is its unreliability of switching due to dust and oxidation of the contacts, and further the necessity of mechanical adjustment when placing the sensor in operation.
Further, there are known sensors which detect the movement of the thread by means of piezo-ceramic bimorph elements, which detect vibrations caused by the movement of the thread and in case of the stoppage of the thread this condition is registered by an electronic circuit. The disadvantage of these sensors is their sensitivity to vibrations, which are transmitted from the machine or from its surroundings. In addition, such sensors are quite costly.